This invention relates to a gasket device for statically sealing high pressure and temperature fluids.
As is known, the problem of ensuring a tight seal against leakage and losses at the joints and connections along a fluid conveying line has been solved by employing suitable gaskets between the elements of the line which require static interconnection. Where the fluids being thus conveyed are in a high pressure and temperature condition, the problem of ensuring a tight seal is, of course, more serious as far as the gaskets are concerned.
Current techniques propose several solutions, which are not, however, devoid of drawbacks. In fact, the use of gaskets entirely formed from materials which are conventional for the intended application, such as rubber, elastomers, Teflon, etc., while being satisfactory from the standpoint of the leakproof property, has the serious drawback of providing inadequate flameproof features where the material of the gasket is exposed to the direct action of a hot fluid, and even if gaskets of asbesto or the like fibers are utilized, there occurs in time a progressive deterioration of the same, especially where high operating pressures prevail.
On the other hand, the use of gaskets merely formed from a soft metallic material, such as aluminum, copper, brass, mild steel, and the like, can indeed overcome the problem of gasket deterioration in the presence of hot gases or vapors, but introduces side problems of not negligible import, which originate from the difficulty of providing an effective seal across the metal-to-metal contact area between a flange and gasket, and from the need of accommodating high clamping forces, especially in the instance of high operating pressures, which implies an oversize connective structure.
Also known and utilized are gaskets formed from a corrugated sheet of soft metal, which gaskets are filled, in the hollows left between the corrugations, with a softer non-metallic material effective to improve the sealing properties of the gaskets. However, no effective retentive action is exerted on the latter material while the gasket is installed and subjected to compressive forces, and in most cases there occurs in operation a delamination of the softer material accompanied by a deterioration of the bond between it and the corrugated sheet metal, which results in the necessity of periodically replacing the gasket.
Alternatively, gaskets are also employed comprising a thin metal liner or shell, which partly surrounds or fully encloses an insert, e.g. of graphite-asbesto fibers or other suitable materials. In this case, the metal liner or shell, having either an open side or being completely closed, is arranged to ensure the geometrical integrity of the gasket, but at least across one face of the gasket there still exist a condition of metal-to-metal contact with the mating flanged element, which contact, depending on the nature of the fluid and on the clamping force applied to the gasket, may be insufficient to eliminate the leakage problem.
A partial solution to this problem, namely the metal-to-metal contact, may be provided with a suitable preparation of the surfaces against which the gasket is to rest, or with the use of special adhesive masses or oils for improving the contact, but all these approaches would introduce additional construction and assembling complications which stand far from the functional simplicity sought in such applications.
In the light of the foregoing considerations, it will appear that the solutions thus far proposed to improve the quality of the seal involve substantial manufacturing costs, and provide inferior reliability and durability features.